theme-gcwu-fegc: improved contrast of non-linked h3 in sidenav

1. Matches font-size of non-linked and linked `<h3 class="top-section">`  elements.
1. Improves contrast of non-linked `<h3 class="top-section">` elements (currently set at #666666).

Example of how it looks with the changes is below:

![h3-top-section](https://f.cloud.github.com/assets/2110107/467594/d49ec1f8-b67d-11e2-9947-8c2dbf21031b.png)